1. Field of the Invention
The present invention relates to a method of fabricating a semiconductor structure, and more particularly, to a method of fabricating a semiconductor structure for improving the critical dimension uniformity.
2. Description of the Prior Art
In semiconductor manufacturing processes, in order to transfer an integrated circuit onto a semiconductor wafer, the integrated circuits from a database are first designed as a layout pattern and a photomask is then manufactured according to the layout pattern. Patterns on the photomask may then be able to be transferred to the semiconductor wafer. The steps mentioned above may be regarded as a photolithographic process. The photolithographic processes includes many steps, such as a thin film deposition process, a photoresist coating process, an exposure and develop process, and an etching process. The critical dimension (CD) control of the pattern formed by the photolithographic process mentioned above is very important because the layout pattern has to be extremely accurate for forming delicate integrated circuits so as to align with the patterns of the previous and following steps. There are many causes of CD deviations, and etching uniformity of the etching process should be an important one. The etching uniformity may be influenced by many factors, such as etchant condition, layout pattern, and loading effect. Accordingly, the etching process and/or the layout design have to be modified for improving the etching uniformity and the CD control of the semiconductor structure.